Academic Discussion VS. Practical Application
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- čas přidán 7. 01. 2022
- The academic discussion around primer seating depth has become very spirited. It's very strange to have been talking about this for so many years, and only now to have people start thinking about it and talking about it. By now, many have done their own testing and have seen benefit. Though there are still many that are content to only talk about it. Ok, lets talk about it.
- Sport
Recieved my CPS late last week, measured brass and primers for 4 calibers and 4 different brass mfgs. Loaded tests for each just touching anvil and increased increments of .001 up to .004 crush. Three of the four shot significantly best at .004 crush, the other liked .002 crush. I now think i need to retest with more crush to make sure i can't find even more precision and to validate the previous test. I'm extremely satisfied with the product!
first trip here. very impressed with your intellect ......ill be back
I look forwards to this new toy... I am a graphing nutcase... I am gonna keep track of how many primers this unit will push.. Very likely well over 500K or more, just by the looks of the construction, which is nicely done, I must add... Super excited... Come on Feb...
Back in the days when I was young... "good quality" brass was very difficult to get. We often found ourselves in the position of having to "make a silk purse out of a sow's ear"... The brass of the quality used in National Match ammo wasn't easy to find, and most commercial brass was a hit and miss proposition that changed over time and so the yield was a matter of luck. That meant as often as not we were forced to sort and prep common brass with lots of work to get to what we commonly buy off the shelf today.
There was no public internet yet, so mail order outfits, personal connections, or long drives were required to get hold of bulk brass to sort from. The yield was never guaranteed. At times it was high, but the very next batch could be very low, and that means less than 30% of a batch of one or two thousand was even close to a good starting point before you put more work into it. The rest was given or traded away to folks who didn't care. For this discussion, that included many other dimensions but certainly included the rim thickness and primer pocket dimensions.
There were many folks who spent time with the dimensions Greg is discussing. They were interested in all sort of accuracy games including BR and Highpower, so there was motivation to get an improved performance from the brass that was available because you could not count on getting "match" brass.
I hear what Greg is saying about starting with good quality brass, but have some experience of my own and will wait to hear how the examples Greg mentions turn out. In my own experience, I am far less accepting of primer pocket depth variations and had good success cutting in accurate primer pocket corrections. I would rather not and I am glad that in these days we have good options to start with brass that makes it unnecessary. YMMV
Really interesting discussion. Trying to do better (uniforming primer pockets) makes things worse. I am very interested in the discussion of the depth test procedure because I have never performed one. Can't wait for the video to be released. I also found the discussion made in another video about removing the ejector very interesting. I removed it some time ago, or rather I removed the spring leaving the plug, without thinking on the fact that this can increasing the inconsistency of the distance of the primer from the firing pin. Truly enlightening videos from a technical point of view.
Groundbreaking information! Greg you’re such a great communicator. Thanks for sharing and I greatly anticipate the primer seating depth test.
Thanks for watching!
Yeah, may have to watch that a couple more times to get all of that to sink in. 😆 A graphic may have been nice, but I love your videos and passion.
I use a false chamber made with reamer to check primer depth uniformity. As long as my bump is consistent the primer measurement should tell me how accurate the primer seat is in case
Greg, how do you ensure your primer pockets are "clean"? What criteria are applied to the definition of a "clean" primer pocket? I wet tumble my brass in SS pins (I know you are not a fan of that because of the damage they do to the mouth).. Through the use of a Telong bore camera, I have found that the ss pins clean the pockets better than any other media, including rice. With that said, with the use of the bore camera, I find that the primer pockets are not clean. I say this because when speaking of primer depth seating variations, we are down to .001" to reach optimum seating depth. I'm assuming that the small amount of carbon still in the primer pocket could introduce a variance of .001" or more. What are your thoughts on this, or have i gone way to deep down this rabbit hole?
Respectfully,
Gary
Half a twist of a dulled uniformer with my fingers.
Awesome stuff thank you
Very welcome!
I spent many hours experimenting with an adjustable primer pocket cutter. I made depth gauges to set it and modified a Wilson case trimmer and case holders to hold the brass while the machining was done to the pocket. It was as close to a lathe that wasn't powered by a motor of some sort I could come up with or maybe it should be called a horizontal boring tool. I tried indexing off of the case head and like you said in your discussion there are geographical variations due to the head stamp or other say ejector or extractor damage on fired brass. I tried indexing off of the overall length of the case but the cases have to be all trimmed exactly the same length and the stop was removed from the base of the cutter and depth was adjusted with the Wilson trimmer lathe. I never could achieve a uniform depth there was just too much compounded error like you stated. I never found any brass of any manufacture that was too shallow not saying it never happens I just didn't come across any. The tiny end mill like cutter used in a pocket tool has very little relief for chips so any material that is removed basically stops the cutter up and it must be withdrawn from the pocket and cleaned continuously. About the only positive outcome from this exercise was the pocket measuring tools I made on my lathe to attach to a digital dial indicator. I put the cutters and depth gauges I made in a little box and stashed them in my toolbox. I will say the cases that I modified the pockets have nice shiny square bottoms and to get them looking like that makes them very close to out of spec in depth. My time is better spent now just measuring pocket depth and weeding out any unusual ones. The only thing I stick in the pockets now beside primers is a little brass brush that sweeps the carbon out.
Who makes and what type is the "little brass brush" you using to clean the pockets? I hear a ton of shooters mention they don't clean their primer pockets, yet endless discussions are being made about .0005"-.001" variances in pocket depth etc; I don't get it, you have got to clean the carbon out of your pockets if you are trying to pursue ignition timing. Thank you!
Lots of shooters don’t pursue most things very far.
@@johnkennedy6331 It is a brass brush that Dremel sells. I have several of them and take a small O ring and roll it down the arbor onto the brush so the brush doesn't flare out so much under pressure. It's a trick that bolt jewelers use to keep the brushes they use to a uniform size when jeweling a bolt or other pieces. I have used the RCBS brushes but they are too coarse and don't seem to do anything and could do more damage than good. I usually chuck the brush in my drill press and give the pockets a quick scrubbing before going into a Thumler tumbler for cleaning prior to sizing and the other operations. I final tumble the brass in rice after trimming. It's hard to get that discoloration out of the primer pocket with brushes or polishing media and using an adjustable cutter that makes the pocket deeper to expose fresh brass is just adding more error.
@@perdidocamaronero5400 Thanks Perdido, I'll check out the Dremel brush. I agree, the RCBS brush is way too stiff and does terrible damage to the floor of the primer pocket, it's even worse when used in a drill. I wouldn't worry about the discoloration affecting performance, keeping the brass clean of debris is paramount. I use a pocket profiler (by hand) to loosen the carbon in the pocket; the profiler doesn't touch the bottom and doesn't cut any brass. Once the carbon has been loosened, I clean the brass. If you like your brass nice and shiny, try using Iosso's case cleaner that comes in a little bucket.
www.midwayusa.com/product/1012771171?pid=888624 Maybe Greg will tell us of the special rice he uses to clean his brass...?
@@johnkennedy6331 I wrote a reply to Greg's comment on giving a dull uniformer a half twist and I totally agree to that somehow my reply didn't post.🤔 The length of the set uniformers that are available must be slightly longer than the industry standard for pocket depths otherwise they wouldn't do anything that's why I was messing with the adjustable version. I quickly found you could set the stop collar too deep and it was a pain to try to get a light cut. I put that stuff away. I have been tumbling in fine walnut actually it's lizard litter and using the cheapest rice I can find for the final polish. It gets in the flash holes but I clear them with compressed air. Don't leave the rice in the vibrator out in an open shop that isn't climatized I did and the rice breaks down over time and makes a mess if you tumble in it. It coats the brass with starch and a white dust that's hard to remove I finally threw the brass into my sonic cleaner and it came off. As cheap as rice is I change it often.
Thank you for the knowledge
My pleasure!
Do you have any testing showing that the timing is more important than the amount of anvil compression?
Timing or the distance from the firing pin to the base of the primer would only seem to change the speed at which the firing pin hits the primer. I don’t know this as a fact but a couple thousandths of an inch would probably be almost the exact same firing pin velocity.
Changing the initial amount of anvil compression by a couple thousandths would seem to make a much bigger difference in how the primer reacts. This is just my guess though.
Depending on which one is most important would significantly change where the best place to measure from is.
Test it! Report back! As I said, it’s time for people to start doing their own shooting. 😉
@@primalrights I would if I could. Unfortunately I don’t have the measurement equipment to do this. I bet you do though…
Should most case base imperfections be gone after the first firing?
It will often take 3-6 to fully form
Ok, now this is OCD abuse 😆